diff options
Diffstat (limited to 'lib/floatuntixf.c')
| -rw-r--r-- | lib/floatuntixf.c | 74 |
1 files changed, 39 insertions, 35 deletions
diff --git a/lib/floatuntixf.c b/lib/floatuntixf.c index a28db10f6..5a48cafec 100644 --- a/lib/floatuntixf.c +++ b/lib/floatuntixf.c @@ -1,28 +1,31 @@ -//===-- floatuntixf.c - Implement __floatuntixf ---------------------------===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// This file implements __floatuntixf for the compiler_rt library. -// -//===----------------------------------------------------------------------===// +/* ===-- floatuntixf.c - Implement __floatuntixf ---------------------------=== + * + * The LLVM Compiler Infrastructure + * + * This file is distributed under the University of Illinois Open Source + * License. See LICENSE.TXT for details. + * + * ===----------------------------------------------------------------------=== + * + * This file implements __floatuntixf for the compiler_rt library. + * + * ===----------------------------------------------------------------------=== + */ #if __x86_64 #include "int_lib.h" #include <float.h> -// Returns: convert a to a long double, rounding toward even. +/* Returns: convert a to a long double, rounding toward even. */ -// Assumption: long double is a IEEE 80 bit floating point type padded to 128 bits -// tu_int is a 128 bit integral type +/* Assumption: long double is a IEEE 80 bit floating point type padded to 128 bits + * tu_int is a 128 bit integral type + */ -// gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee | -// 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm +/* gggg gggg gggg gggg gggg gggg gggg gggg | gggg gggg gggg gggg seee eeee eeee eeee | + * 1mmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm | mmmm mmmm mmmm mmmm mmmm mmmm mmmm mmmm + */ si_int __clzti2(ti_int a); @@ -32,17 +35,18 @@ __floatuntixf(tu_int a) if (a == 0) return 0.0; const unsigned N = sizeof(tu_int) * CHAR_BIT; - int sd = N - __clzti2(a); // number of significant digits - int e = sd - 1; // exponent + int sd = N - __clzti2(a); /* number of significant digits */ + int e = sd - 1; /* exponent */ if (sd > LDBL_MANT_DIG) { - // start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx - // finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR - // 12345678901234567890123456 - // 1 = msb 1 bit - // P = bit LDBL_MANT_DIG-1 bits to the right of 1 - // Q = bit LDBL_MANT_DIG bits to the right of 1 - // R = "or" of all bits to the right of Q + /* start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx + * finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR + * 12345678901234567890123456 + * 1 = msb 1 bit + * P = bit LDBL_MANT_DIG-1 bits to the right of 1 + * Q = bit LDBL_MANT_DIG bits to the right of 1 + * R = "or" of all bits to the right of Q + */ switch (sd) { case LDBL_MANT_DIG + 1: @@ -54,26 +58,26 @@ __floatuntixf(tu_int a) a = (a >> (sd - (LDBL_MANT_DIG+2))) | ((a & ((tu_int)(-1) >> ((N + LDBL_MANT_DIG+2) - sd))) != 0); }; - // finish: - a |= (a & 4) != 0; // Or P into R - ++a; // round - this step may add a significant bit - a >>= 2; // dump Q and R - // a is now rounded to LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits + /* finish: */ + a |= (a & 4) != 0; /* Or P into R */ + ++a; /* round - this step may add a significant bit */ + a >>= 2; /* dump Q and R */ + /* a is now rounded to LDBL_MANT_DIG or LDBL_MANT_DIG+1 bits */ if (a & ((tu_int)1 << LDBL_MANT_DIG)) { a >>= 1; ++e; } - // a is now rounded to LDBL_MANT_DIG bits + /* a is now rounded to LDBL_MANT_DIG bits */ } else { a <<= (LDBL_MANT_DIG - sd); - // a is now rounded to LDBL_MANT_DIG bits + /* a is now rounded to LDBL_MANT_DIG bits */ } long_double_bits fb; - fb.u.high.low = (e + 16383); // exponent - fb.u.low.all = (du_int)a; // mantissa + fb.u.high.low = (e + 16383); /* exponent */ + fb.u.low.all = (du_int)a; /* mantissa */ return fb.f; } |